Battery electrode and manufacturing method thereof

Abstract

The present invention relates to an electrode composition comprising PTFE and at least one copolymer of maleic anhydride and diisobutylene, its method of preparation, and its use in the manufacture of electrochemical cell components.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Patent Application Publication No. 23305314.9, filed March 9, 2023, the entire contents of which are incorporated herein by reference for all purposes. [Technical Field]

[0002] The present invention relates to an electrode composition comprising at least one copolymer obtained from the polymerization of at least one ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic polycarboxylic acid or anhydride thereof with at least one ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer, a method for preparing the same, and its use for the manufacture of electrochemical cell components. [Background technology]

[0003] To date, electrodes for lithium secondary batteries are primarily manufactured by a wet process that involves preparing a slurry in which electrode active materials, additives, and binders are dispersed in a solvent or aqueous medium, and processing the slurry to form an electrode film.

[0004] Dry electrode processes were developed to reduce the time-consuming and costly drying procedures required by the wet processes described above.

[0005] Typical dry processes utilize the fibrillating properties of certain polymers to provide a matrix for the embedded conductive material. Some polymers in the fluoropolymer family, such as polytetrafluoroethylene (PTFE), are particularly inert and stable in common electrode solvents used in secondary batteries, even those with organic solvents at high operating or storage temperatures. Therefore, the stability of electrodes made with PTFE can be higher than those made with other binders.

[0006] For example, a dry electrode fabrication process can involve combining a PTFE binder with the active electrode material in powder form and calendering to form an electrode film. However, while PTFE has good adhesion to the electrode active material, it has difficulty adhering to the current collector.

[0007] A method for improving the adhesion of PTFE to a current collector and an electrode active material by using a combination of PTFE and tetrafluoroethylene / hexafluoropropylene copolymer (FEP) as a binder to achieve a material having the melting point of FEP (240 to 270°C) or higher is known in the art (JP 2000149954 A). However, a special heat treatment device is required to heat the electrode film to a temperature above the melting point of FEP, specifically, 280°C or higher, which is inconvenient from an energy standpoint.

[0008] Another drawback of PTFE is its limited electrochemical stability on the anode side, which can lead to polymer decomposition and lower coulombic efficiency when used as a binder for the anode. Furthermore, when the anode is made of silicon, one of the important obstacles to overcome is the significant volume change that occurs in the silicon active material when absorbing (expanding) and desorbing (shrinking) lithium during charge-discharge cycles. These substantial shrinkage-swelling cycles impose high mechanical stress on the anode layer, causing circuit damage and poor contact, resulting in reduced capacity and ultimately failure of the electrochemical cell.

[0009] One approach to overcoming the unique challenges associated with silicon is to create a self-healing mechanism within the binder matrix by incorporating weak bonding interactions that allow for some degree of reversibility. These unstable bonds can then be broken under stress but reform upon relaxation without irreparable damage to the active material particles. Unfortunately, PTFE cannot interact closely with the active material through such bonding interactions, making it a poor binder candidate for silicon-rich anodes.

[0010] Many approaches are being pursued to develop next generation binders that are also compatible with silicon anodes.

[0011] There are several polycarboxylate binders and derivatives being pursued, including polyacrylic acid, polyamic acid, polyacrylamide, and other hydrogen-bonding structures.

[0012] The applicant has unexpectedly discovered that certain polymers obtained by copolymerization of at least one monomer having maleic anhydride with at least one olefinic hydrocarbon monomer can be used in dry electrode manufacturing processes, particularly in manufacturing processes for silicon-rich anodes, so that electrodes can be provided by a highly efficient process. Summary of the Invention

[0013] Thus, the present specification provides a method for producing an electrode for an electrochemical cell [electrode (E)], comprising the steps of: i) providing at least one polymer [polymer (A)] resulting from the polymerization of at least one monomer (I) and at least one monomer (II), said monomers being Monomer (I): an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic polycarboxylic acid or anhydride, Monomer (II): an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer; The corresponding process; - ii) dry-mixing, in the absence of a solvent, at least one electrode active material (AM), a polymer (A) as defined above, and optionally at least one conductive agent to obtain a dry electrode-forming composition [composition (C)]; - iii) feeding the composition (C) obtained in step ii) into a press to form a self-supporting dry film; and - iv) applying the dry film to a conductive substrate to form an electrode; A method is provided that includes:

[0014] In another aspect, the present invention provides an electrode (E) for a secondary battery, obtainable by the method defined above.

[0015] The applicant has discovered that the addition of polymer (A) is particularly effective in ensuring improved adhesion to PTFE when used as a binder for electrodes for secondary batteries, and as a result, polymer (A) can be conveniently used as the sole binder or in a blend with PTFE to obtain high adhesion.

[0016] Thus, the present specification provides a binder composition [binder (B)] for use in preparing an electrode for an electrochemical device, comprising: a. Polytetrafluoroethylene (PTFE); b. at least one polymer (A) as defined above; A binder composition [binder (B)] is provided, which comprises:

[0017] The applicant has surprisingly discovered that the processability of binder (B) makes it suitable for fabricating electrodes by dry processing or extrusion at low temperatures, thereby providing electrodes by a very efficient process.

[0018] Therefore, in another aspect, the present invention provides a method for producing an electrode for an electrochemical cell [electrode (E1)], comprising the steps of: step I) combining polytetrafluoroethylene (PTFE) with the polymer (A) defined above to obtain the binder (B); - step II) dry-mixing at least one electrode active material (AM), the binder (B) obtained in step I), and optionally at least one conductive agent in the absence of a solvent to obtain a dry electrode-forming composition [composition (C1)]; - step III) feeding the composition (C1) obtained in step II) into a press to form a self-supporting dry film; and - step IV) applying the dry film to a conductive substrate to form an electrode; A method is provided that includes:

[0019] In another aspect, the present invention provides an electrode (E1) for a secondary battery, obtainable by the method defined above.

[0020] In a further aspect, the present invention relates to an electrochemical device, such as a secondary battery or a capacitor, comprising at least one electrode (E) or electrode (E1) as defined above. DETAILED DESCRIPTION OF THE INVENTION

[0021] In the context of the present invention, the term "weight percent" (wt%) refers to the content of a particular component in a mixture, calculated as the ratio between the weight of the particular component and the total weight of the mixture. When referring to repeating units derived from a certain monomer in a polymer / copolymer, weight percent (wt%) refers to the ratio between the weight of the repeating units of that monomer to the total weight of the polymer / copolymer. When referring to the total solids content of a liquid composition, weight percent (wt%) refers to the ratio between the weights of all non-volatile components in the liquid.

[0022] As used herein, the terms "adhere" and "adhesion" refer to two layers being permanently joined to one another via their contact surfaces.

[0023] The term "electrochemical device" is intended herein to mean an electrochemical cell / assembly comprising a positive electrode, a negative electrode, and a liquid electrolyte, wherein a single-layer or multi-layer separator is in contact with at least one surface of one of the electrodes. Non-limiting examples of suitable electrochemical devices include, inter alia, secondary batteries, particularly alkaline or alkaline-earth secondary batteries such as lithium-ion batteries, lead-acid batteries, and capacitors, particularly lithium-ion-based capacitors and electric double-layer capacitors (supercapacitors). Non-limiting examples of electrochemical cells include, inter alia, batteries, preferably secondary batteries, electric double-layer capacitors.

[0024] For the purposes of the present invention, "secondary battery" is intended to denote a rechargeable battery. Non-limiting examples of secondary batteries include alkaline or alkaline earth secondary batteries, among others.

[0025] Polymer (A) Polymer (A) is a copolymer derived from the polymerization of at least one monomer (I) and at least one monomer (II), Monomer (I) is an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic polycarboxylic acid or anhydride, Monomer (II) is an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer.

[0026] As used herein, "copolymer" is intended to refer to a polymer having two or more different monomer units. The copolymer may be a terpolymer having three or more different monomer units, or may have four or more different monomer units. The copolymer may be a random copolymer, a gradient copolymer, or a block copolymer formed by a controlled polymerization process. Preferably, the copolymer is formed by a free radical or anionic polymerization process, which may be any polymerization method known in the art, including, but not limited to, solution polymerization or suspension polymerization, and may be carried out in bulk or semi-bulk polymerization.

[0027] The monomer (I) preferably has the following formula: (R 1 )(R 2 )C=C(R 3 )-COOR X (Wherein radical R 1 , R 2 and R 3 are the same or different and are C1-C groups which may optionally contain a hydrogen atom or a -COOH group. 10 R is selected from the group consisting of a hydrocarbon radical and a -COOH group; 1 , R 2 and R 3 at least one of which is not a hydrogen atom; R X is a C1-C alkyl group containing a hydrogen atom or at least one carboxyl functional group 20 R is selected from hydrocarbon moieties; 1 and R 2 Any of the -COOH groups may optionally be at least partially replaced by a group COOR X may form an anhydride together with It is a monomer of

[0028] According to a preferred embodiment of the present invention, the monomer (I) has the following formula: (R 4 )HC=C(R 5 )COORX (In the formula, R 4 is a hydrogen atom, a -COOH group, or a -(CH2) n -COOH group (n is 1 to 4), or a C1 to C4 alkyl radical; R 5 is a hydrogen atom, -(CH2) m -COOH group (m is 1 to 4), or a C1 to C4 alkyl radical; R 4 and R 5 at least one of which is not a hydrogen atom; R X is as defined above) The corresponding polycarboxylic acids or carboxylic acid anhydrides are:

[0029] Preferably, R 4 is selected from the group consisting of a hydrogen atom, a —COOH group or a (CH)—COOH group, and a methyl radical; R 5 is selected from the group consisting of a hydrogen atom, —CHCOOH, or a methyl radical; R 4 and R 5 At least one of the is not a hydrogen atom.

[0030] According to a more specific embodiment, the monomer (I) is selected from the group consisting of citraconic acid, maleic acid, fumaric acid, or itaconic acid, their esters or anhydrides; (meth)acryloyloxyalkyl succinic acids, such as (meth)acryloyloxyethyl succinic acid and (meth)acryloyloxypropyl succinic acid.

[0031] More preferably, monomer (I) is maleic anhydride.

[0032] The monomer (II) preferably has the following formula: (R 6 )(R 7 )C=CH 2 (Wherein radical R 6 and R 7are the same or different and are a hydrogen atom or a linear or branched, aliphatic or cyclic, saturated or ethylenically unsaturated C1-C 10 radicals selected from the group consisting of It is a monomer of

[0033] More specifically, the radical R 6 and R 7 are the same or different and are a hydrogen atom or a saturated, linear or branched, aliphatic or cyclic C1-C 10 The radical is selected from the group consisting of:

[0034] Preferably, the monomer (II) is selected from the group consisting of ethylene, propylene, 1-butene, isobutylene, n-1-pentene, 2-methyl-1-butene, n-1-hexene, 2-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, diisobutylene (or 2,4,4-trimethyl-1-pentene), 2-methyl-3,3-dimethyl-1-pentene.

[0035] In one embodiment of the present application, polymer (A) is preferably a copolymer of maleic anhydride and diisobutylene.

[0036] In one embodiment, polymer (A) is more specifically a copolymer of 40 mol % to 60 mol % of monomer (I) and 60 mol % to 40 mol % of monomer (II).

[0037] In a preferred embodiment of the present invention, polymer (A) is a copolymer of maleic anhydride and diisobutylene containing about 40 mol % to 60 mol %, preferably about 50 mol %, of maleic anhydride monomer units and 60 mol % to 40 mol %, preferably about 50 mol %, of diisobutylene monomer units.

[0038] The molecular weight Mw of the copolymer used as polymer (A) is usually 10,000 Da to 500,000 Da, preferably 15,000 Da to 75,000 Da.

[0039] Polymer (A) is prepared by polymerizing a mixture of monomer (I) and monomer (II), optionally in the presence of other α,β-ethylenically unsaturated monomers such as acrylonitrile, N-vinylimidazole, N-vinylpyrrolidone, vinylphosphonic acid.

[0040] The polymer (A) suitably has an average particle size (D50) in the range of 5 to 250 μm.

[0041] The average particle size of the positive electrode active material can be measured by a particle size distribution analyzer for dynamic light scattering.

[0042] Polymer (A) may be at least partially further neutralized to provide at least a portion of the carboxylic acid or anhydride moieties in salt form.

[0043] Thus, in one embodiment of the present invention, there is provided a composition (C) containing a copolymer (polymer (A)) of monomer (I) and monomer (II) at least partially in the form of a salt.

[0044] Therefore, the preparation of polymer (A) may further comprise a step of neutralizing at least a portion of the anhydride or carboxyl groups with a salt containing a monovalent or divalent cation [salt (SA)] in a suitable solvent.

[0045] The salt (SA) may be any salt capable of neutralizing an anhydride group or a carboxylic acid group, which is preferably an alkali metal cation, an alkaline earth metal cation, a tertiary or quaternary ammonium cation, more preferably Na + , K. + , Li + and / or a salt capable of providing a quaternary ammonium cation.

[0046] Electrode active material (AM) For the purposes of the present invention, the term "electrode active material" is intended to mean a compound that can incorporate or insert alkali or alkaline earth metal ions into its structure during the charging and discharging stages of an electrochemical device and then substantially release them. The electrode active material preferably can incorporate or insert lithium ions and release them.

[0047] The nature of the electrode active material (AM) varies depending on whether the composition is used in the manufacture of the negative electrode (anode) or the positive electrode (cathode).

[0048] When forming a positive electrode for a lithium-ion secondary battery, the electrode active material can include a composite metal chalcogenide of the formula LiMQ2, where M is at least one metal selected from transition metals such as Co, Ni, Fe, Mn, Cr, and V, and Q is a chalcogen such as O or S. Among these, it is preferable to use a lithium-based composite metal oxide of the formula LiMO2, where M is the same as defined above. Preferred examples of these include LiCoO2, LiNiO2, LiNi x Co 1-x O2, where 0 < x < 1, and spinel-structured LiMn2O4 can be mentioned.

[0049] As an alternative form, when forming a positive electrode for a lithium-ion secondary battery, further, the electrode active material is of the formula M1M2(JO4) f E 1-fwherein M1 is lithium and may be partially substituted by another alkali metal corresponding to less than 20% of the M1 metal; M2 is a transition metal having an oxidation level of +2 selected from Fe, Mn, Ni or mixtures thereof and may be partially substituted by one or more additional metals having an oxidation level of +1 to +5, inclusive, corresponding to less than 35% of the M2 metal; JO4 is any oxyanion; J is any of P, S, V, Si, Nb, Mo or combinations thereof; E is a fluoride, hydroxide or chloride anion; and f is the mole fraction of the JO4 oxyanion, typically comprised between 0.75 and 1.

[0050] M1M2(JO4) as defined above f E 1-f The electroactive material is preferably phosphate-based and may have an ordered or modified olivine structure.

[0051] More preferably, the electrode active material when forming a positive electrode is a compound represented by the formula Li 3-x M' y M'' 2-y (JO4)3, where 0≦x≦3, 0≦y≦2, M′ and M″ are the same or different metals, at least one of which is a transition metal, JO4 is preferably PO4 which may be partially substituted with another oxyanion, and J is any of S, V, Si, Nb, Mo, or a combination thereof. Even more preferably, the electrode active material has the formula Li(Fe x Mn 1-x )PO4, where 0≦x≦1, and x is preferably 1 (i.e., lithium iron phosphate of formula LiFePO4).

[0052] As a further alternative, when forming a positive electrode for a lithium ion secondary battery, the electrode active material is garnet-type inorganic particles Li7La3Zr2O 12 (LLZO), or the general formula Li x La yZr z A w O 12 (wherein - A represents one or more dopants selected from the group consisting of Al, Ga, Nb, Fe, Nd, Pt, Ta, W, Mo, Hf, Si, Ca, Sr, Ba, Ge, and mixtures thereof, preferably selected from the group consisting of Al, Ga, Nb, Fe, Nd, Pt, Ta, W, and mixtures thereof, more preferably selected from the group consisting of Al, Ga, W, and mixtures thereof, - w, x, y, and z are positive numbers including various combinations of integers and fractions or decimals, - 0 < y ≤ 3, preferably 2 ≤ y ≤ 3, preferably 2.5 ≤ y ≤ 3, - 0 < z ≤ 2, preferably 1 ≤ z ≤ 2, preferably 1.5 ≤ z ≤ 2, - 0 ≤ w ≤ 0.5, preferably 0 ≤ w ≤ 0.35, more preferably 0 ≤ w ≤ 0.25, - x is derived from the electrical neutrality of the garnet structure) doped LLZO inorganic particles having and combinations thereof may be included.

[0053] When forming a positive electrode for a sodium-ion secondary battery, the electrode active material may include a Na-based layered transition metal oxide, a Prussian blue analog, and a polyanion-type material.

[0054] In some embodiments, the active material is a Na-based layered transition metal oxide classified as O3-, P2-, and P3-types depending on the stacking order of the oxygen layers. The P2-type structure generally corresponds to the general formula NaxMO2 (where M represents a transition metal ion such as Co, Mn, etc., and x is 2 / 3).

[0055] In some embodiments, the active material is Na 0.81 Fe[Fe(CN)6] 0.79□0.21 , NaFe2(CN)6, Na1 .63 Fe 1.89 (CN)6, Na 1.72 MnFe(CN)6, Na 1.76 Ni 0.12Mn 0.88 [Fe(CN)6] 0.98 , Na2Ni x Co 1-x Fe(CN)6 (0≦x≦2 and 0≦y<1, such as Na2CoFe(CN)6), where A is an alkali metal ion, P is an N-coordinated transition metal ion, and R is a C-coordinated transition metal ion; □ is the general formula A, where [R(CN)6] is the vacancy x P[R(CN)6] 1-y□y It is a Prussian blue analogue (PBA) of .mH2O.

[0056] In some other embodiments, the active material comprises a series of tetrahedral anionic units (XO4) n - and their derivatives (X m O 3m+1 ) n- having the general formula Na x M y (XO4) n (wherein X = S, P, Si, As, Mo, or W, and M is a transition metal) are polyanion-type materials. 0.7 Phosphates such as FePO4 or NaMnPO4, NaMPO4; x Sodium (sodium) superionic conductors with NASICON-type structure of M2(XO4)3 (where 1≦x≦4, M=V, Fe, Ni, Mn, Ti, Cr, Zr...; X=P, S, Si, Se, Mo...), such as single transition metal types such as Na3V2(PO4)3 (NVP), Na3Cr2(PO4)3, Na3Fe2(PO4)3; binary transition metal types such as Na2VTi(PO4)3, Na3FeV(PO4)3, Na4MnV(PO4)3, Na3MnZr(PO4)3, Na3MnTi(PO4)3, Na4Fe3(PO4)2(P2O7)(NFPP); pyrophosphates Na2FeP2O7, Na2MnP2O7, Na2CoP2O7, Na 4-x Fe 2+x / 2 (P2O7)2(2 / 3≦x≦7 / 8), e.g., Na 3.12 Fe 2.44 (P2O7)2 or Na 3.32 Fe2.34 (P2O7)2, Na2(VO)P2O7, Na7V3(P2O7)4; fluorophosphates NaVPO4F, Na2CoPO4F, Na2FePO4F, Na2MnPO4F, Na3(VO 1-x PO4)2F 1+2x (0≦x≦1), such as Na3(VOPO4)2F or Na3V2(PO4)2F3(NVPF); fluorosulfates, such as NaMSO4F (M=Fe, Co, Ni); mixed phosphates / pyrophosphates of the general formula Na4M3(PO4)2(P2O7) (M represents a transition metal), such as NaNa4Mn3(PO4)2(P2O7), Na4Co3(PO4)2(P2O7), Na4Ni3(PO4)2(P2O7), Na4Fe3(PO4)2(P2O7)(NFPP), Na7V4(P2O7)4(PO4); sulfates, such as Na2Fe2(SO4)3, Na 2+2x Fe 2-x (SO4)3, Na 2+2x Co 2-x (SO4)3, Na 2+2x Mn 2-x (SO4)3 (0≦x≦1); silicates of the general formula Na2MSiO4 (M=Mn, Fe, Co, and Ni).

[0057] In some preferred embodiments, the active material is preferably NaVPOF, NaCoPOF, NaFePOF, NaMnPOF, Na(VO 1-x PO4)2F 1+2x where 0≦x≦1, for example a fluorophosphate selected from the list consisting of Na3(VOPO4)2F or Na3V2(PO4)2F3(NVPF).

[0058] When forming a negative electrode for a secondary battery, the electrode active material may preferably comprise a material selected from the group consisting of one or more carbon-based materials and one or more silicon-based materials.

[0059] In some embodiments, the carbon-based material may be selected from graphite, such as natural or artificial graphite, graphene, or carbon black.

[0060] These materials may be used alone or as a mixture of two or more thereof.

[0061] The carbon-based material is preferably graphite.

[0062] The silicon-based compound may be one or more selected from the group consisting of chlorosilanes, alkoxysilanes, aminosilanes, fluoroalkylsilanes, silicon, silicon chloride, silicon carbide, and silicon oxide.

[0063] More specifically, the silicon-based compound may be silicon oxide or silicon carbide.

[0064] Silicon oxides include, in particular, lithiated materials for forming Li4SiO4 and Li2SO3, as disclosed in WO 2015 / 063979, having the formula SiO x Particles having (0.5≦x≦1) may be included.

[0065] When present in the electrode active material, the silicon-based compound is included in an amount ranging from 1 to 60% by weight, preferably from 5 to 30% by weight, based on the total weight of the electroactive compound.

[0066] Composition (C) may further comprise one or more optional conductivity-imparting additives, which may be added to improve the conductivity of the resulting electrode produced from composition (C).

[0067] Conductive agents for batteries are known in the art.

[0068] Examples may include carbon-based materials such as carbon black, graphite fine powder, carbon nanotubes, graphene or fibers, or fine powders or fibers of metals such as nickel or aluminum. The optional conductive agent is preferably carbon black. Carbon black is available, for example, under the brand names Super P® or Ketjenblack®.

[0069] If present, the conductive agent is different from the carbon-based material described above.

[0070] The amount of the optional conductive agent is preferably 0 to 30 wt % of the total solids in the electrode-forming composition. In particular, in the case of a cathode-forming composition, the amount of the optional conductive agent is typically 0 to 10 wt %, more preferably 0 to 5 wt %, of the total solids in the composition.

[0071] For anode-forming compositions that do not include a silicon-based electroactive compound, the optional conductive agent is typically present in an amount of from 0 wt. % to 5 wt. %, more preferably from 0 wt. % to 2 wt. %, of the total amount of solids in the composition, while for anode-forming compositions that include a silicon-based electroactive compound, it has been found beneficial to incorporate a larger amount of optional conductive agent, typically from 0.5 to 30 wt. % of the total amount of solids in the composition.

[0072] In step ii) of the method of the present invention, mixing the electrode active material (AM), the polymer (A) defined above, and the optional at least one conductive agent is carried out by dry mixing these components without adding solvents, liquids, processing aids, etc. to the particle mixture. Dry mixing can be carried out, for example, in a mill, mixer, or blender (such as a V-blender equipped with a high-strength stirring rod or other alternative equipment as further described below) until a uniform dry mixture is formed. Those skilled in the art will recognize, after reading this specification, that mixing times may vary based on batch size, materials, particle size, density, and other properties and still remain within the scope of the present invention.

[0073] In step iii) of the process of the present invention, the powdery dry mixture obtained in step ii) is subjected to a mechanical compression step to obtain a self-supporting dry film.

[0074] The compaction of the dry mixture obtained in step ii) can be carried out as a mechanical compaction, for example by means of a roller compactor or a tablet press, but it may also be carried out as a rolling, build-up or by any other technique suitable for this purpose.

[0075] The mechanical compression step may be associated with a thermal consolidation step. The combination of pressure and heat treatment allows for thermal consolidation at a lower temperature than if it were carried out alone.

[0076] In one embodiment, the mechanical compaction step is carried out by pressing, suitably by pressing the dry mixture obtained in step ii) between two metal foils. Preferably, the mechanical compaction step is carried out by applying a compaction pressure of 5 to 50 MPa, preferably 10 to 30 MPa.

[0077] The compression step is conveniently carried out at a temperature of not more than 200°C, preferably below 180°C.

[0078] In step iv), the dry film obtained in step iii) is applied onto a conductive substrate to form an electrode.

[0079] The sheet of substrate material may comprise a metal foil, particularly an aluminum foil.

[0080] Due to the improved adhesion of composition (C), the dry film obtained in step iii) can be applied onto a conductive substrate without the need for a primer or an adhesive layer.

[0081] Steps i) through iv) can be performed as a single step or as separate steps, and some of the steps can be functionally separated and / or combined during the implementation of some embodiments.

[0082] Polymer (A) may conveniently be used as the sole binder in the preparation of electrodes by the process of the present invention or may be used in a blend with PTFE.

[0083] Therefore, according to another aspect of the present invention, there is provided a method for producing an electrode for an electrochemical cell [electrode (E1)], comprising the steps of: step I) combining polytetrafluoroethylene (PTFE) with the polymer (A) defined above to obtain the binder (B); - step II) dry-mixing, without solvent, at least one electrode active material (AM), a binder (B) as defined above, and optionally at least one conductive agent to obtain a dry electrode-forming composition [composition (C1)]; - step III) feeding the composition (C1) obtained in step II) into a press to form a self-supporting dry film; and Step IV) applying the dry film to a conductive substrate to form an electrode. A method is provided that includes:

[0084] In the context of the present invention, the term "PTFE" means a polymer obtained from the polymerization of tetrafluoroethylene (TFE).

[0085] However, it is understood that the PTFE polymer may also contain small amounts of one or more comonomers, such as, but not limited to, hexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(propyl vinyl ether), and perfluoro-(2,2-dimethyl-1,3-dioxole), provided that the latter do not significantly adversely affect the inherent properties of the tetrafluoroethylene homopolymer, such as its thermal and chemical stability. Preferably, the amount of such comonomers does not exceed about 3 mol%, more preferably less than about 1 mol%; a comonomer content of less than 0.5 mol% is particularly preferred. When the total comonomer content is greater than 0.5 mol%, it is preferred that the amount of perfluoro(alkyl vinyl ether) comonomer be less than about 0.5 mol%. PTFE homopolymer is most preferred.

[0086] PTFE suitable for use in preparing the binder (B) of the present invention can be in the form of a powder or in the form of a latex.

[0087] PTFE in powder form can be obtained by solidifying a PTFE lattice by cryogenic solidification or by electrolytic solidification with the addition of an electrolyte. See, for example, U.S. Patent No. 6,790,932. Preferred examples of electrolytes are: - Aluminum sulfate (Al2(SO4)3) at a concentration of 2 g / l calculated based on the amount of water in the coagulation vessel, - Ammonium carbonate ((NH4)2CO3) at a concentration of 8 g / l calculated based on the amount of water in the coagulation vessel, or - Nitric acid (HNO3), 25 ml of a 65% solution calculated based on the amount of water in the coagulation vessel.

[0088] Alternatively, the PTFE powder may be obtained from a PTFE lattice in the form of a gel by coagulation with an electrolyte as described above. The gel may be obtained according to US Patent Nos. 6,790,932 and 6,780,966.

[0089] After coagulation has taken place, the polymer is washed with demineralized water at room temperature. After coagulation and washing, the PTFE powder obtained therefrom is then dried.

[0090] PTFE lattices are generally obtained by dispersion or emulsion polymerization.

[0091] PTFE in powder form generally has a particle size of 1 to 1600 microns, preferably 100 to 800 microns, and more preferably 400 to 700 microns.

[0092] Particle size can be expressed relative to D50, which is the corresponding particle size when the cumulative percentage reaches 50%. D50 is also called median particle size or median diameter. For example, for a powder sample with D50=5 μm, it means that 50% of the particles are larger than 5 μm and 50% of the particles are smaller than 5 μm.

[0093] The binder (B) is obtained by mixing PTFE and polymer (A), both in powder form, or by mixing a PTFE latex with a polymer (A) latex, followed by co-coagulation and isolation by a cryogenic or electrolytic procedure.

[0094] To obtain the desired polymer ratio in the blend, the dry content of the PTFE latex and / or polymer (A) latex can be estimated by drying 50 grams of the polymer latex at 200° C. in a thermobalance.

[0095] Generally, the weight ratio PTFE / polymer (A) will be between 95 / 5 wt / wt and 30 / 70 wt / wt. Those skilled in the art will select the most suitable weight ratio taking into account the target final properties of the binder (B).

[0096] Applicants have surprisingly discovered that the amount of polymer (A) added to PTFE does not affect its ability to fibrillate.

[0097] The amount of binder (B) that can be used in the electrode-forming composition (C1) is influenced by various factors. One such factor is the surface area and amount of the active material and the surface area and amount of the conductivity-imparting additive added to the electrode-forming composition. These factors are believed to be important because the binder particles provide a bridge between the conductive material particles, keeping them in contact.

[0098] Composition (C1) comprises one or more electrode active materials (AM) as defined above.

[0099] The dry blending step II) fibrillates the binder particles to produce fibrils that ultimately form the matrix supporting the resulting composition of matter. The resulting dough-like material can be calendered multiple times to produce a conductive film of desired thickness and density. Blending can be provided by subjecting the mixture to an extruder.

[0100] The same details provided above for steps A) through D) apply to steps I) through IV), respectively.

[0101] Steps I)-IV) can be performed as a single step or as separate steps, and some of the steps can be functionally separated and / or combined during the implementation of some embodiments.

[0102] The composition (C) or the composition (C1) obtained in step B) or step II) of the process according to the invention may further comprise at least one sulfide-based solid electrolyte.

[0103] When the composition (C) or the composition (C1) used in the process according to the invention comprises at least one sulfide-based solid electrolyte or at least one solid electrolyte based on garnet-type inorganic particles, the present invention provides an electrode suitable for use in a solid-state battery [electrode (ESS)] obtained by the process defined above.

[0104] Thus, in one embodiment, the present invention provides a method for producing an electrode for a solid state battery (ESS), comprising: a) providing a polymer (A) as defined above; - b) dry-mixing, without solvent, at least one electrode active material (AM), the polymer (A) prepared in step A) defined above, at least one sulfide-based solid electrolyte or at least one garnet-type inorganic particle-based solid electrolyte, and optionally at least one conductive agent, to obtain a dry electrode-forming composition [composition (C')]; - c) feeding the composition (C') obtained in step B) into a press to form a self-supporting dry film; and - d) applying the dry film to a conductive substrate to form an electrode. The present invention provides a method comprising:

[0105] The same details provided above for steps A) to D) apply to steps a) to d), respectively.

[0106] In another aspect, the present invention provides a method for producing an electrode for a solid-state battery [Electrode (ESS-1)], comprising: step I') combining polytetrafluoroethylene (PTFE) with the polymer (A) defined above to obtain the binder (B); - step II') dry-mixing at least one electrode active material (AM), the binder (B) defined above, at least one sulfide-based solid electrolyte, and optionally at least one conductive agent in the absence of a solvent to obtain a dry electrode-forming composition [composition (C1')]; - step III') feeding the composition (C1') obtained in step B) into a press to form a self-supporting dry film; and - Step IV') Applying the dry film to a conductive substrate to form an electrode The present invention provides a method comprising:

[0107] The same details provided above for steps A) to D) apply to steps I') to IV'), respectively.

[0108] As used herein, the phrase "sulfide-based solid electrolyte" refers to a Li + Refers to inorganic solid-state materials that conduct ions but are substantially electronically insulating.

[0109] In the present invention, the term "sulfide-based solid ionically conductive inorganic particles" is not particularly limited as long as it is a solid electrolyte material containing sulfur atoms in its molecular structure or composition.

[0110] The sulfide-based solid, ionically conductive inorganic particles preferably contain Li, S, and an element of Groups 13 to 15, such as P, Si, Sn, Ge, Al, As, Sb, or B, in order to increase Li-ion conductivity.

[0111] The sulfide-based solid, ionically conductive inorganic particles according to the present invention are preferably selected from the group consisting of: - Li 10 SnP2S 12Lithium tin phosphorus sulfide ("LSPS") materials such as; - Formula (Li2S) x -(P2S5) y where x+y=1 and 0≦x≦1, Li7P3S 11 , Li7PS6, Li4P2S6, Li 9.6 P3S 12 and lithium phosphosulfide ("LPS") materials such as glasses, crystals, or glass-ceramics of the type Li3PS4; - Li2CuPS4, Li 1+2x Zn 1-x PS4 (wherein 0≦x≦1), Li 3.33 Mg 0.33 P2S6 and Li 4-3x Sc x doped LPS such as P2S6 (where 0≦x≦1); - Expression Li x P y S z Lithium Phosphorus Sulfide Oxygen (“LPSO”) material of formula O, where 0.33≦x≦0.67, 0.07≦y≦0.2, and 0.4≦z≦0.55; - Li 10 SnP2S 12、 Li 10 GeP2S 12, Li 10 SiP2S 12 , and lithium phosphorus sulfide materials with X being Si, Ge, Sn, As, or Al, such as Li2S-P2S5-SnS ("LXPS"); - Lithium Phosphorus Sulfide Oxygen ("LXPSO"), with X being Si, Ge, Sn, As, or Al; - Li2SiS3, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 and lithium silicon sulfide ("LSS") materials, such as Li2S-SiS2-Al2S3; - Lithium borosulfide materials such as Li3BS3 and Li2S-B2S3-LiI; - Li 0.8 Sn 0.8 S 2、 Li4SnS4, Li 3.833 Sn 0.833 As 0.166 Lithium tin sulfide and lithium arsenide materials such as S4, Li3AsS4-Li4SnS4 and Ge-substituted Li3AsS4; - General formula Li a PS b X c (wherein X represents at least one halogen element selected from the group consisting of Cl, Br, and I or a combination thereof; a represents a number from 2.0 to 7.0; b represents a number from 3.5 to 6.0; and c represents a number from 0 to 3.0), such as Li4PS4Cl 、 Li7P2S8Cl, and Li7P2S8I.

[0112] In a more preferred embodiment, the sulfide-based solid, ionically conductive inorganic particles have the general formula Li a PS b X c and more specifically, argyrodite-type sulfide-based materials of the formula Li6PS5X (wherein X is Cl, Br, or I).

[0113] In another preferred embodiment, the argyrodite-type sulfide-based material of formula Li6PS5Y is, for example, Li 6-x PS 5-x Cl 1+x (0≦x≦0.5) or are sulfur and / or lithium deficient or doped with heteroatoms.

[0114] Particularly preferred sulfide solid electrolytes are LPS materials, LSPS materials and argyrodite-type sulfide-based materials.

[0115] The electrode (E), electrode (E1) and electrode (ESS) of the present invention are particularly suitable for use in electrochemical devices, especially secondary batteries.

[0116] In one aspect, the present invention provides an electrochemical device that is a secondary battery, the secondary battery comprising: - Positive and negative electrodes A secondary battery comprising: At least one of the positive electrode and the negative electrode is an electrode (E), (E1) or (ESS) according to the present invention.

[0117] In a further object, the present invention provides a solid-state battery comprising a composite solid electrolyte membrane, a positive electrode, and a negative electrode, A solid-state battery is provided in which at least one of the negative electrode or the positive electrode is an electrode (ESS) according to the present invention.

[0118] The secondary battery of the present invention is preferably an alkaline secondary battery or an alkaline earth secondary battery.

[0119] The secondary battery of the present invention is more preferably a lithium ion secondary battery.

[0120] Electrochemical devices according to the present invention can be fabricated by standard methods known to those skilled in the art.

[0121] To the extent that the disclosure of any patent, patent application, and publication incorporated herein by reference contradicts the statement of this application to the extent that a term may be unclear, the statement shall control.

[0122] The present invention will now be described with reference to the following examples, the purposes of which are merely illustrative and are not intended to limit the scope of the invention. [Example]

[0123] raw materials Polymer (A-1): Maleic anhydride / diisobutylene copolymer neutralized with NaOH, available from Solvay as Geropon® T36. silicon oxide, commercially available from Shin-Etsu Chemical Co., Ltd., KSC-1064, theoretical capacity approximately 2100 mAh / g; graphite, GHDR 15-4 commercially available from Imerys SA; carbon black, commercially available as SC45 from Imerys SA; carbon black, commercially available as SC65 from Imerys SA; PTFE: PTFE homopolymer powder having a specific gravity of 2160 measured according to ASTM D792 and a rheometric pressure of 9.50 MPa measured according to ASTM D4895; Lithium iron phosphate, LFP, available as Life Power manufactured by Johnson Matthey; Galden HT80, commercially available from Solvay Materials;

[0124] Anode according to the dry process of the present invention: A dry mixture of 5.41 g of graphite, 1.36 g of silicon oxide, and 0.072 g of SC45 was prepared by grinding the powders in an electric mortar for 10 minutes.

[0125] 5 ml of Galden HT80 was added to the powder mixture and the composite was mixed in an electric mortar for 1 minute. A homogeneous paste was obtained.

[0126] 0.29 g of polymer (A-1) powder and 0.07 g of PTFE were added to the homogeneous paste together with 4 ml of Galden HT80, and mixed in a mortar and pestle mill for 5 minutes to obtain a homogeneous composite.

[0127] The composite was then manually manipulated to fibrillate the polymer and obtain an overall bonded free-standing film.

[0128] The film was calendered to reduce the thickness to less than 200 μm.

[0129] The resulting negative electrode had the following composition: 75.2% by weight graphite, 18.8% by weight silicon, 4% by weight polymer (A-1), 1% by weight PTFE, and 1% by weight carbon black.

[0130] In this way, the negative electrode NE1 was obtained.

[0131] A sample of the negative electrode NE1 was placed between two copper current collectors and preheated in a press at 150° C. for 10 minutes. Then, 160 bar was applied for 10 minutes to laminate NE1 to the current collectors at a temperature of 150° C. and a pressure of 160 bar. The press was then allowed to cool to room temperature without releasing the pressure.

[0132] Dry-process cathode according to the present invention A dry mixture of 6.48 g of LFP and 0.36 g of SC65 was prepared by grinding the powders in an electric mortar for 10 minutes.

[0133] 4 ml of Galden HT80 was added to the powder mixture and the complex was mixed in an electric mortar for 1 minute to obtain a homogeneous paste.

[0134] 0.18 g of polymer (A-1) powder and 0.18 g of PTFE were added to the homogeneous paste together with 3 ml of Galden HT80, and mixed in a mortar and pestle mill for 5 minutes to obtain a homogeneous composite.

[0135] The composite was then manually manipulated to fibrillate the polymer and obtain an overall bonded free-standing film.

[0136] The film was calendered to reduce the thickness to less than 200 μm.

[0137] The resulting positive electrode had the following composition: 90% by weight of LFP, 2.5% by weight of polymer (A), 2.5% by weight of PTFE and 5% by weight of carbon black.

[0138] In this way, positive electrode 1 (PE1) was obtained.

[0139] The PE1 sample was placed between two aluminum current collectors and preheated in a press at 150° C. for 10 minutes. 160 bar was then applied for 10 minutes to laminate the PE1 to the current collectors at a temperature of 150° C. and a pressure of 160 bar. The press was then allowed to cool to room temperature without releasing the pressure.

[0140] Dry Process Anodes - Comparison A dry mixture of 5.41 g of graphite, 1.36 g of silicon oxide, and 0.072 g of SC45 was prepared by grinding the powders in an electric mortar for 10 minutes.

[0141] 5 ml of Galden HT80 was added to the powder mixture and the complex was mixed in an electric mortar for 1 minute to obtain a homogeneous paste.

[0142] 0.36 g of PTFE was added to the homogeneous paste along with 4 ml of Galden HT80 and mixed in a mortar and pestle mill for 5 minutes to obtain a homogeneous composite.

[0143] The composite was then manually manipulated to fibrillate the polymer and obtain an overall bonded free-standing film.

[0144] The film was calendered to reduce the thickness to less than 200 μm.

[0145] The resulting negative electrode had the following composition by weight: 75.2% graphite, 18.8% silicon, 2.5% PTFE, and 1% carbon black.

[0146] In this way, the electrode CE1 was obtained.

[0147] The CE1 sample was placed between two copper current collectors and preheated in a press at 150° C. for 10 minutes. 160 bar was then applied for 10 minutes to laminate the CE1 to the current collectors at a temperature of 150° C. and a pressure of 160 bar. The press was then allowed to cool to room temperature without releasing the pressure.

[0148] Dry Process Cathodes - Comparison A dry mixture of 6.48 g of LFP and 0.36 g of SC65 was prepared by grinding the powders in an electric mortar for 10 minutes.

[0149] 4 ml of Galden HT80 was added to the powder mixture and the complex was mixed in an electric mortar for 1 minute. A homogeneous paste was obtained.

[0150] 0.36 g of PTFE was added to the homogeneous paste along with 3 ml of Galden HT80 and mixed in a mortar and pestle mill for 5 minutes to obtain a homogeneous composite.

[0151] The composite was then manually manipulated to fibrillate the polymer and obtain an overall bonded free-standing film.

[0152] The film was calendered to reduce the thickness to less than 200 μm.

[0153] The resulting positive electrode had the following composition: 90 wt. % LFP, 2.5 wt. % PTFE, and 5 wt. % carbon black.

[0154] In this way, the electrode CE2 was obtained.

[0155] The CE2 sample was placed between two aluminum current collectors and preheated in a press at 150° C. for 10 minutes. 160 bar was then applied for 10 minutes to laminate the CE2 to the current collectors at a temperature of 150° C. and a pressure of 160 bar. The press was then allowed to cool to room temperature without releasing the pressure.

[0156] Adhesion evaluation and measurement Adhesion evaluation and measurements were carried out between the samples laminated as described above and the foil in the three-layer structure (metal foil / film / metal foil) obtained after lamination according to ASTM D 1876. The adhesion levels are reported in Table 1 below.

[0157] A higher value for peel strength indicates better intimate adhesion between the polymer and the current collector.

[0158] [Table 1]

[0159] No adhesion was observed for the PTFE powder when used alone in the preparation of films by compression, either between two aluminum foils or between two copper foils.

Claims

1. A method for producing an electrode [electrode (E)] for an electrochemical cell, comprising the steps of: i) providing at least one polymer [polymer (A)] resulting from the polymerization of at least one monomer (I) and at least one monomer (II), said monomers being: Monomer (I): an ethylenically unsaturated, linear or branched, aliphatic, cyclic or aromatic polycarboxylic acid or anhydride, Monomer (II): an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer, a process corresponding to - ii) dry-mixing, in the absence of solvent, at least one electrode active material (AM), a polymer (A) as defined above, and optionally at least one conductive agent to obtain a dry electrode-forming composition [composition (C)]; - iii) feeding the composition (C) obtained in step ii) into a press to form a self-supporting dry film; and - iv) applying the dry film to a conductive substrate to form an electrode; A method comprising:

2. The monomer (I) has the following formula: (R １ )(R ２ )C=C(R ３ )-COOR Ｘ (Wherein radical R １ , R ２ and R ３ are the same or different and may optionally contain a hydrogen atom, a —COOH group, １ ~C １０ is selected from the group consisting of a hydrocarbon radical and a —COOH group; R １ , R ２ , and R ３ at least one of which is not a hydrogen atom; R Ｘ is a hydrogen atom or a C containing at least one carboxyl functional group １ ~C ２０ selected from hydrocarbon moieties; R １ and R ２ Any of the —COOH groups may optionally be at least partially replaced by the group COOR Ｘ may form an anhydride together with The method of claim 1 , wherein the monomer is

3. 3. The method of claim 2, wherein the monomer (I) is selected from the group consisting of citraconic acid, maleic acid, fumaric acid, or itaconic acid, esters or anhydrides thereof; (meth)acryloyloxyalkyl succinic acids, such as (meth)acryloyloxyethyl succinic acid and (meth)acryloyloxypropyl succinic acid.

4. Monomer (II) is of the following formula: (R ６ )(R ７ )C=CH ２ (Wherein radical R ６ and R ７ are the same or different and are a hydrogen atom or a linear or branched, aliphatic or cyclic, saturated or ethylenically unsaturated C １ ~C １０ radicals selected from the group consisting of The method according to any one of claims 1 to 3, wherein the monomer is

5. 5. The process according to claim 4, wherein the monomer (II) is selected from ethylene, propylene, 1-butene, isobutylene, n-1-pentene, 2-methyl-1-butene, n-1-hexene, 2-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, diisobutylene (or 2,4,4-trimethyl-1-pentene), 2-methyl-3,3-dimethyl-1-pentene, preferably monomer (II) is diisobutylene.

6. The process of any one of claims 1 to 5, wherein the polymer (A) is a copolymer of maleic anhydride and diisobutylene monomer units.

7. The method according to any one of claims 1 to 6, wherein the polymer (A) is at least partially in the form of a salt.

8. An electrode (E) for a secondary battery obtainable by the method according to any one of claims 1 to 7.

9. A binder composition [binder (B)] for use in preparing an electrode for an electrochemical device, comprising: a. Polytetrafluoroethylene (PTFE); b. at least one monomer (I) and at least one monomer (II); at least one polymer (A) obtained from the polymerization of Monomer (I): ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic polycarboxylic acids or anhydrides, Monomer (II): an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer, a polymer (A) corresponding to A binder composition [binder (B)] comprising:

10. 10. The binder (B) according to claim 9, wherein the weight ratio PTFE / polymer (A) is comprised between 95 / 5 wt / wt and 30 / 70 wt / wt.

11. A method for producing an electrode for an electrochemical cell [electrode (E1)], comprising the steps of: step I) combining polytetrafluoroethylene (PTFE) with at least one polymer (A) to obtain a binder (B), said at least one polymer (A) resulting from the polymerization of at least one monomer (I) and at least one monomer (II), said monomers being: Monomer (I): ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic polycarboxylic acids or anhydrides, Monomer (II): an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer, Corresponding to, Obtaining a binder (B); Step II) dry-mixing the at least one electrode active material (AM), the binder (B) obtained in Step I), and optionally at least one conductive agent in the absence of a solvent to obtain a dry electrode-forming composition [composition (C1)]; step III) feeding said composition (C1) obtained in step II) into a press to form a self-supporting dry film; and - step IV) applying said dry film to a conductive substrate to form an electrode; A method comprising:

12. 12. An electrode (E1) for a secondary battery obtainable by the method according to claim 10 or 11.

13. 1. A method for manufacturing an electrode for a solid-state battery (ESS), comprising: a) providing at least one polymer (A) resulting from the polymerization of at least one monomer (I) and at least one monomer (II), said monomers being Monomer (I): ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic polycarboxylic acids or anhydrides, Monomer (II): an ethylenically unsaturated, linear or branched, aliphatic, cyclic, or aromatic hydrocarbon monomer, To respond to b) dry-mixing, in the absence of a solvent, at least one electrode active material (AM), the polymer (A) prepared in step a), at least one sulfide-based solid electrolyte or at least one garnet-type inorganic particle-based solid electrolyte, and optionally at least one conductive agent, to obtain a dry electrode-forming composition [composition (C')]; c) feeding the composition (C') obtained in step b) into a press to form a self-supporting dry film; and - d) applying said dry film to a conductive substrate to form an electrode. A method comprising:

14. An electrode for a secondary battery (ESS) obtainable by the method according to claim 13.

15. An electrochemical device such as a secondary battery or a capacitor, wherein at least one of a positive electrode or a negative electrode is the electrode (E) according to claim 8, the electrode (E1) according to claim 12, or the electrode (ESS) according to claim 14.

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